Fender Twin Reverb Amp - Repair, Recap and Restore - Part 1 of 2
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- เผยแพร่เมื่อ 28 ส.ค. 2024
- Another Fender Tube AMP on the bench, this time a perfect condition Fender Twin Reverb. This amp seems to blow fuses when power is supplied, therefore ending up in my hands.
Wow, quite amazing, I may be the first one in this amp, as it would seem. This however lends itself toward the problem as the original Electrolytic caps cant possible be good. The explosion under the cover confirms my findings. This is a complete recap job (so far as electrolytic caps go).
I can never bring myself to remove the old caps without testing them, so naturally they go on the Genrad and the IT-11 for expected awful results. But hey, why not. This also included all of the Electrolytic caps needed to the Cathode bias, each was removed and replaced. Finally the last electrolytic cap in the bias was swapped AND upgraded to 100uf.
I did also check all of the coupling caps; listed and tested in the IT-11, and they did turn out to be in perfect order so they were not replaced.
Not everything is fun. Like having to measure every resistor, but yeah...... funny thing though, there were more out of tolerance resistors than I expected. So swap-outs definitely needed to be made before continuing. Some resistors off as much as 80%
Funny how one POT was found to have whiskers all over it and none of the others. a quick observation.
Naturally tube testing is done, this is one of the last videos to exclusively use the Century tester. Not that i'm getting rid of it, but the Hickok 6000 will be talking over soon. All tubes tested good.
With that the VARIAC dial up of the unit begins...... aaaand its shut down. It seems the plate voltage appears regardless of the standby switch position. Looks like its time to troubleshoot a short. Not only that but the voltage on the plate is the rectifier voltage. I wont spoil it, the troubleshooting and issue is found in the video.
I did break out the Pevono PS 305-H to search for the short instead of using mains voltage and the lethal voltage in the AMP.
The short was found, time to continue.... Thats for another video...
This gentleman is properly trained and knows what he is doing.
Opens dog house and touches filter caps without discharging. LOL
If those grid stopper resistors need changing in old Fenders I never use carbon comp. The heat rises up into the chassis and they are going to take a beating just like the originals. Metal film is quieter and less sensitive to heat degradation, as I'm sure you know. Purists be damned. Great work!
You would be surprised, though in many cases I upgrade the materials there ae cases where there is an insistence on the original parts, which from a collector perspective can be understandable.
Awesome Video Retro Tech & Electronics!
Thanks!
@ 13:30 the technical name for those whiskers is dendrites. They can form when certain types of metal start to corrode. They can especially reak havoc in an electronic circuit by shorting out everything in its path.
Thanks for sharing, funny only one was so effected. all of those pots are really past their prime though.
hey, I noticed my bassman has pots with these dendrites (though not as severe). how would u recommend I clean them?
13:34 - It looks *magnetized* !
You are smart as hell!!
You too!
Thanks for this! One just like it just landed in my shop, awesomely unmolested! What a treat
Question: you replaced the 50 MFD bias supply cap with a 100. Schematic indicates it should be a 25. any other considerations or concerns around making this change?
That cap upgraded is the only universally recommended change for original amps coming in for a recap job or repair.
6:45- where is the other end of the black lead connected to?
Black is tied to the red lead going to the left side of the capacitor, just out of frame
Phillips made tubes(Mullard, Amperex etc.) almost always flash on startup. Not a sign of a bad tube.
A startup flash is never a good thing for longevity. Thermistors can help...
What temperature do you run your iron?
I have this same amp and i'm thinking of getting new capacitors for it. Is it an expensive fix to replace them? also what are some of the symptoms of bad filter caps?
If you dont know how to do it, have someone else do it. Its not worth dying over...
@@retrotechandelectronics I would never attempt to install caps myself since i don't have the know how or knowledge to do so. I just wanted to know what i'd be up against in regards to price for the parts needed.
@@JHarrison49 Typical, never an answer to the questions. Just watch Lee Jacksons videos.
excellent
Thanks!
Hello! How many watts Rms does each speaker resist?
Depends on how the tubes are biased.
@@retrotechandelectronics I edited my question. it would be how many watts each resists. Thank you.
Don’t throw up on the bench!🤮 Good God, what a mess that would be.🤢
If that was a guitar I'd say it was fake.
Do you think that thing has just been stored in a giant tupperware or something for 50+ years?
This is what collector amps look like.
@@retrotechandelectronics I can see why they fetch big bucks. I'm not sure I appreciate why people care so much about how it looks (vs how it sounds) but each to their own. :)
Please leave the music off of your videos.
No. Let me know if there was a anything else you need.
@@retrotechandelectronics well done!